title: Dietary glutamate signal evokes gastric juice excretion in dogs.
abstract: BACKGROUND
  Dietary-free L-glutamate (Glu) in the stomach interacts with specific Glu receptors (T1R1/T1R3 and mGluR1-8) expressed on surface epithelial and gastric gland cells. Furthermore, luminal Glu activates the vagal afferents in the stomach through the paracrine cascade including nitric oxide and serotonin (5-HT).
  
  
  OBJECTIVE
  To elucidate the role of dietary Glu in neuroendocrine control of the gastrointestinal phase of gastric secretion.
  
  
  METHODS
  In Pavlov or Heidenhain gastric pouch dogs, secretion was measured in the pouch while monosodium glutamate (MSG) was intubated into the main stomach alone or in combination with liquid diets.
  
  
  RESULTS
  In both experimental models, supplementation of the amino acid-rich diet with MSG (100 mmol/l) enhanced secretions of acid, pepsinogen and fluid, and elevated plasma gastrin-17. However, MSG did not affect secretion stimulated by the carbohydrate-rich diet and had no effect on basal secretion when applied in aqueous solution. Effects of MSG were abolished by denervation of the stomach and proximal small intestine with intragastrically applied lidocaine and partially suppressed with the 5-HT(3) receptor blocker granisetron.
  
  
  CONCLUSIONS
  Supplementation of amino acid-rich liquid diets with MSG enhances gastrointestinal phase secretion through neuroendocrine pathways which are partially mediated by 5-HT. Possible mechanisms are discussed.
authors.affiliation: Laboratory of Physiology of Digestion, Pavlov Institute of Physiology of the Russian Academy of Sciences, St. Petersburg, Russia.
authors.forename: Raisa
authors.initials: R
authors.lastname: Khropycheva
authors.forename: Julia
authors.initials: J
authors.lastname: Andreeva
authors.forename: Hisayuki
authors.initials: H
authors.lastname: Uneyama
authors.forename: Kunio
authors.initials: K
authors.lastname: Torii
authors.forename: Vasiliy
authors.initials: V
authors.lastname: Zolotarev
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D004032:Diet; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004285:Dogs; D005260:Female; D005744:Gastric Acid / Q000378:metabolism; D005753:Gastric Mucosa / Q000294:innervation / Q000378:metabolism*; D005755:Gastrins / Q000097:blood; D008297:Male; D008962:Models, Theoretical; D009490:Neurosecretory Systems / Q000502:physiology; D010435:Pepsinogens / Q000378:metabolism; D044406:Receptors, Serotonin, 5-HT3 / Q000502:physiology; D012970:Sodium Glutamate / Q000008:administration & dosage / Q000494:pharmacology*; D013270:Stomach / Q000187:drug effects* / Q000294:innervation / Q000502:physiology
chemical_list: D000596:Amino Acids; D004040:Dietary Carbohydrates; D005755:Gastrins; D010435:Pepsinogens; D044406:Receptors, Serotonin, 5-HT3; C013550:gastrin 17; D012970:Sodium Glutamate